Overactive bladder (“OAB”) and urinary incontinence (“UI”) affect over 16% of the American population each year, or approximately 34 million men and women. Outside of the United States, OAB and UI affects over 46 million Europeans. The economic cost of OAB and UI is estimated to be in excess of $12 billion a year in the United States alone.
Due to the social stigmas attached to OAB and UI and to misunderstandings related to the symptoms associated with OAB and UI, only 40% of the affected individuals in the United States seek medical treatment. Of those 13.6 million Americans seeking medical treatment, nearly 30% or 4 million individuals are reportedly unsatisfied with their current therapy.
Known treatments for OAB and UI include exercise and behavioral modifications, pharmacological therapies, surgical intervention and neuromodulation, but each of these treatments exhibits severe limitations.
Exercise and behavioral modifications often require patients to adhere to stringent routines, including scheduled voiding, maintenance of a bladder diary, and intense exercise regimens. While this type of treatment may be a viable option for a small group of highly dedicated individuals, its daily impact on a person's life makes it unattractive for most patients.
Pharmacological intervention is the most widely prescribed therapy for OAB and UI. Unfortunately, patients often suffer from side effects related to their drug therapies. Such side effects are sometimes serious and are particularly pronounced in elderly patient populations that tend to use a plurality of medications. In addition, approximately 30% of all patients subjected to pharmacological therapies appear to be dissatisfied with the efficacy of their prescribed treatments.
Surgical intervention IS extremely invasive and often results in a long-term requirement for catheterization that may become permanent in some instances. The negative impact of these procedures on the patient's quality of life and their high expense make surgical intervention a recommended option only when all other treatment options have been exhausted.
Neuromodulation is another available therapy for OAB and UI. In general, pulsed electromagnetic stimulation (“PES”) has proven to have beneficial effects in a variety of medical applications. The related scientific principle is that an electric current passing through a coil generates an electromagnetic field, which induces a current within a conductive material placed inside the electromagnetic field.
More particularly, PES has been shown to be an effective method of stimulating a nerve positioned within the electromagnetic field, thereby affecting a muscle controlled by that nerve. For example, in the paper titled “Contactless Nerve Stimulation and Signal Detection by Inductive Transducer” presented at the 1969 Symposium on Application of Magnetism in Bioengineering, Maass et al. disclosed that a nerve threading the lumen of a toroid could be stimulated by a magnetic field of 0.7 Volt peak amplitude and a 50 μs duration in a monitor wire, and that such stimulation could generate a contraction of major leg muscles in anesthetized mammals.
Various attempts were made to use PES for treating a variety of ailments. For example, U.S. Pat. No. 4,548,208 to Niemi discloses an apparatus for inducing bone growth by generating an electric current in the body through the external application of an electromagnetic field. Such apparatus includes opposing clamps disposed on a limb and may optionally include feedback coils and a microprocessor for sensing the magnetic field, so to avoid an overcurrent mode. Therefore, this apparatus optimizes the magnetic field on the basis of measurements of the generated magnetic field.
U.S. Pat. No. 4,940,453 to Cadwell discloses a method and apparatus for magnetically stimulating the neural pathways of a higher level organism. In this invention, a sinusoidally fluctuating current flow is created through a coil that overlies neurons to be stimulated, and frequency of the current flow and frequency of the magnetic field produced by the coil predetermined to correspond to the time constant of the neurons to be stimulated. Sensors for sensing coil conditions, such as coil temperature, may also be included.
U.S. Pat. No. 5,000,178 to Griffith discloses an electrical to electromagnetic transducer for applying electromagnetic energy to damaged parts of a living body by directing electromagnetic radiation to a certain damaged body part. Electromagnetic radiation is initially generated by a dipole consisting of a bar of high permeability material wrapped with an electrically conductive coil. Magnetic fields, which are generated away from the damaged body part, intersect a conductive shield and establish eddy currents, which in turn generate magnetic fields opposite and nearly equal to the magnetic fields generated by the electromagnetic source. The resultant electromagnetic fields reinforce the electromagnetic field directed towards the damaged body part and diminish the electromagnetic field directed away from the damaged body part.
U.S. Pat. No. 5,014,699 to Pollack et al. discloses a non-invasive, portable electromagnetic therapeutic method and apparatus for promoting the healing of damaged or diseased living tissue, including fractured bone. These method and apparatus involve generating a signal that has a series of substantially symmetric voltage cycles of bursted pulses with narrow pulse widths of 0.5 to 20 microseconds, and further involve converting the signal into an electromagnetic field extending into an area that contains tissue to be healed. This invention provides for no feedback on the efficiency of the applied stimulation.
In a paper titled “Selective Stimulation and Blocking of Sacral Nerves: Research Setup and Preliminary Results,” published in Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Vol. 13, No. 2, 1991, Wijkstrda et al. used an external pulsed magnetic coil to stimulate a peripheral nerve for the treatment of urinary incontinence. The authors used a large magnetic field produced by a single coil to ensure that the nerve was fired and the resulting nerve conduction was frequently painful or intolerable. In addition, coil alignment was problematic because an internally implanted coil was utilized, which had to be aligned with the fully external magnetic field to stimulate the nerve. Due to the difficulty in positioning the device, the practical application of this therapy does not permit home healthcare usage without a preset alignment and monitoring of the nerve, and no provision was made to insure that the nerve was actually being stimulated or to adjust the device in response to commonly occurring physiologic and anatomic variations in nerve locations.
U.S. Pat. No. 5,181,902 Erickson et al. and U.S. Pat. No. 5,314,401 to Tepper disclose pulsed electromagnetic field (“PEMF”) transducer systems usable to perform PEMF therapies (such as after spinal fusion) by generating flux-aided electromagnetic fields. The drive electronics includes a PEMF processor that executes a PEMF program for controlling the activation of the electromagnetic fields (field strength and cycle).
In a paper titled: “Magnetic Stimulation of the Bladder in Dogs” presented at the 1993 AAEM Annual Meeting, the abstract of which was published in the Muscle & Nerve issue of October 1993, Lin et al. disclosed that magnetic stimulation could be employed to stimulate the cortex, spinal nerves and peripheral nerves of dogs through direct trans-abdominal stimulation of the detrusor muscles or through stimulation of the lumbosacral roots.
As shown, however, there has been no provision made to measure the efficacy of PES treatment, causing patients to be treated improperly, either by an insufficient or excessive exposure to PES. Other attempts to monitor PES dosage exhibit serious drawbacks. For example, U.S. Pat. No. 5,518,495 to Kot discloses an apparatus for the treatment of arthritis utilizing a magnetic field therapy, which includes an adjustable voltage source that is connected to a source of line voltage and a coil connected to the adjustable voltage source. This apparatus has no feedback system to advise a healthcare provider of the efficiency of the treatment.
U.S. Pat. No. 5,984,854 to Ishikawa et al. discloses a method for treating urinary incontinence based on delivering a train of current pulses through one or more magnetic stimulation coils so to induce a train of magnetic flux pulses, which then induce an eddy current within the body and stimulates a group of pelvic floor muscles, the pudendal nerve, the external urethral sphincter, or the tibial nerve. While this method includes the use of pulsed electromagnetic for treating urinary incontinence, no specific components are envisioned to facilitate the placement of the magnetic coils over a targeted region of the body or a system for monitoring the efficiency of the therapy being applied.
U.S. Pat. No. 6,086,525 to Davey et al. discloses a magnetic nerve stimulator that includes a core constructed from a material having a high field saturation having a coil winding disposed thereon. A thyrister capacitive discharge circuit pulses the device, and a rapidly changing magnetic field is guided by the core, preferably made from vanadium permendur.
U.S. Pat. No. 6,701,185 to Burnett et al. also discloses an electromagnetic stimulation device that includes a plurality of overlapping coils, which can be independently energized in a predetermined sequence such that each coil will generate its own independent electromagnetic field and significantly increase the adjacent field. Unfortunately, none of these patents provides a system for monitoring the efficiency of the therapy in progress, either with respect to the proper positioning of the winding over the area to be treated or of the intensity of the magnetic field to be applied.
Other PES therapies require the implantation of devices into the patient, with the consequent discomfort, risk and cost to the patient. For example, U.S. Pat. No. 6,735,474 to Loeb et al. discloses a method and system for treating UI and/or pelvic pain by injecting or laparoscopically implanting one or more battery-or radio frequency-powered microstimulators that include electrodes placed beneath the skin of the perineum and/or adjacent the tibial nerve.
U.S. Pat. No. 6,941,171 to Mann et al. describes a method and a system for treating incontinence, urgency, frequency, and/or pelvic pain that includes implantation of electrodes on a lead or a discharge portion of a catheter adjacent the perineal nerve(s) or tissue(s) to be stimulated. Stimulation pulses, either electrical or drug infusion pulses, are supplied by a stimulator implanted remotely through the lead or catheter, which is tunneled subcutaneously between the stimulator and stimulation site.
Other PES therapies involve the use of electrodes placed on or beneath the skin of a patient. Recent data on invasive, needle-based PES of the posterior tibial nerve in individuals with OAB and UI indicates that PES can modulate bladder dysfunction through its action on the pudendal nerve and the sacral plexus, which provide the major excitatory input to the bladder.
In a paper titled “Percutaneous Tibial Nerve Stimulation via Urgent® PC Neuromodulation System—An Emerging Technology for managing Overactive Bladder,” which was published in Business Briefing: Global Surgery 2004, CystoMedix, Inc. disclosed that peripheral tibial nerve stimulation (“PTNS”) had been found effective in treating OAB. The disclosed procedure involved the use of electrode and generator components, including a small 34-gauge needle electrode, lead wires and a hand-held electrical generator. However, the procedure requires the permanent implantation of an electrical stimulation device in the patient. One estimate put the cost of treatment at nearly $14,000 with additional routine care costs of $593 per patient per year. Additionally, risks of battery failure, implant infection, and electrode migration led to a high re-operation rate and made this procedure unattractive.
U.S. Pat. No. 7,117,034 to Kronberg discloses a method for generating an electrical signal for use in biomedical applications that includes two timing-interval generators. In this invention, skin-contact electrodes may be placed over an area of interest and a microprocessor may direct timing and sequencing functions, although such timing and sequencing functions are not related to the actual efficacy of the treatment while treatment is being performed.
U.S. Patent Application Publication No. 2005/0171576 to Williams et al. discloses an electro-nerve stimulation apparatus that includes a pulse generator, a first electrically conductive, insulated lead wire, a second electrically conductive, insulated lead wire, an electrically conductive transcutaneous electrode and an electrically conductive percutaneous needle electrode. Connected to one end of the first and second lead wires is a connector for electrically coupling with the pulse generator. In this invention, a percutaneous needle electrode is inserted through the skin in proximity to the desired internal stimulation site and electric stimulation is employed, rather than pulsed electromagnetic stimulation. Moreover, the Williams invention does not contemplate mechanisms for facilitating use of the device by an untrained user, nor a monitoring of the applied therapy.
A neuromodulation alternative is a posterior tibial nerve stimulator, often referred to as SANS, but as is the case with other forms of neuromodulation, this procedure is invasive in nature and requires the insertion of a needle five centimeters into the patient's ankle region to stimulate the posterior tibial nerve. This procedure also requires a minimum of twelve sessions for initial treatment, possibly with additional sessions required for maintenance.
Also, therapies involving the use of traditional insertable or implantable percutaneous needles require penetration into deeper tissues and carry with them the added risk of infection, while causing pain and discomfort to the patient. This often results in ineffective treatment and or reduced patient compliance.
Additionally, some existing techniques for cooling coils include limitations and disadvantages. For example, some cooling techniques require air to first be cooled, e.g., refrigerated, which involves the use of additional components and parts and could increase cost. Some cooling devices utilize low flow rates and fail to prevent rapid rises in temperature, such that coils must be powered down frequently to prevent overheating damage. As a result, large treatment gaps and low rep rates are often required during therapy that utilizes such devices. Also, heated air is often vented in the direction of the patient due to the configuration of existing devices and necessary flow patterns. Because the vented air can reach high temperatures, this could pose a danger to patients. These cooling deficiencies can limit the load, power and running time at which coils may be operated.